#include <bits/stdc++.h>
using namespace std;

class Solution
{
public:
    int main()
    {
        int n;
        cin >> n;
        if (n == 0)
        {
            cout << "0.00";
            return 0;
        }
        if (n == 1)
        {
            cout << "1.00";
            return 0;
        }
        long long last1 = 1;
        long long last2 = 0;
        long long result = 0;
        for (int i = 2; i <= n; ++i)
        {
            result = last2 + last1;
            last2 = last1;
            last1 = result;
        }
        cout << fixed << setprecision(2) << static_cast<double>(result);
        return 0;
    }
};

#ifndef __LOCAL_TEST__
int main()
{
    return Solution().main();
}
#endif